Siloxane-containing polymers and copolymer have been coated on various thermoplastic articles in order to modify their surface characteristics. For example U.S. Pat. No. 6,500,549 to Deppisch et al. describes coating articles with a biocompatible film comprising polydimethylsiloxane blocks. U.S. Pat. No. 5,589,563 to Ward et al. describes coating articles with surface active endgroup-containing polymers that include a linear base polymer having covalently bonded surface active endgroups that modify the surface tension of the base polymer. U.S. Pat. No. 6,395,226 to Plunkett describes a coating for microporous hollow fiber membrane blood oxygenators that increases the resistance of the fibers to passage of blood plasma through the micropores; the coating includes an alkoxysilane/alkylsilane copolymer. This approach has the drawback of requiring separate handling and coating steps to coat the surface-modifying copolymer.
It is also known to modify the surface properties of a thermoplastic resin by blending a siloxane-containing polymer with the bulk thermoplastic resin. For example, U.S. Pat. No. 3,686,355 to Gaines et al. describes blends of a base polymer and a surface-modifying additive that may be a polycarbonate-polysiloxane block copolymer. However, the amount of surface-modifying additive required to obtain the desired surface properties often detracts from the desirable optical properties of the base copolymer.
There is therefore a need for polymer blends that exhibit desirable surface properties without requiring a surface coating step and without compromising the desirable optical properties of the base polymer.